The present invention refers to a gas-dynamic pressure wave machine which is destined for the charge air supply of an internal combustion engine, comprising a rotor with cells, a low pressure fresh air inlet channel, a high pressure charge air channel leading to the internal combustion engine, a high pressure exhaust channel coming from the internal combustion engine, and a low pressure exhaust channel, the low pressure exhaust channel and the high pressure exhaust channel being enclosed in a gas enclosure and the low pressure fresh air inlet channel and the high pressure charge air channel being enclosed in an air enclosure.
A pressure wave machine of this kind is known from the prior art, e.g. from CH-A-681 738. It is a first general object of the present invention to improve the efficiency of a gas-dynamic pressure wave machine according to the prior art as it is schematically illustrated in FIG. 1 by means of different measures.
In a gas-dynamic pressure wave machine according to the prior art, comprising four channels and no additional control systems such as pockets, which is used in order to supercharge an internal combustion engine, the pressure wave process can only be adjusted for a single operating speed of the internal combustion engine, i.e. the so-called design point of the pressure wave machine. The use of pockets in the enclosure walls allows a less tuning-sensitive design of the pressure wave machine and a significant extension of its load, speed, and volume range. The disadvantage of this method is that in the range of untuned performance, the pressure wave process is diverted to secondary processes which cannot yield optimum efficiency. The result is an increase of the losses caused by such secondary processes in the pockets, e.g. inflowing and outflowing gases and the production of pressure and expansion waves in the pockets.
The transition from the so-called primary process, also called compression pocket process, to the principal process, i.e. the tuned process, causes disturbances in the pressure wave process which cause scavenging disruptions and thus ranges of increased recirculation of exhaust gas into the charge air. In order to prevent an increased recirculation in these ranges as well as during starting, an inlet leading to the gas pocket, either in the form of a milled sill or of a controlled inlet as disclosed in the above-mentioned document, must be provided, which however produces further losses due to a diversion of high pressure energy into the low pressure process.
In the case of low flow rates and low temperatures, i.e. during starting, idle running, or under partial load, the recirculation sensitivity strongly increases. Under these conditions, standard pressure wave machines run in an untuned range where the energy level is too low to allow an undisturbed pressure wave process. In standard machines, in order to make this range operable, a part of the exhaust gases is deviated to gas pockets prior to the admission of the high pressure exhaust gas to the rotor in order to improve the scavenging of the rotor, either by means of a fixed feed or by means of the variable feed disclosed in CH-A-681 738. A disadvantage of this system is that the build-up of the charging pressure is substantially reduced since a part of the exhaust gas which is normally available for the high pressure process is diverted to the low pressure process.
On the background of this prior art, it is a first object of the invention to provide a pressure wave machine having an improved efficiency in low flow rate and low temperature conditions without the use of gas pockets. This object is attained by a pressure wave machine wherein the high pressure exhaust channel is enlarged on the rotor side and comprises means allowing to vary the enlargement without forming a ridge.
Another object of the present invention is to improve the cold start properties of a pressure wave machine in such a manner that a regulation by means of gas pockets or recesses in the enclosure of the pressure wave machine can be partially or entirely omitted. This object is attained by a pressure wave machine wherein a heating device is provided between the outlet of the internal combustion engine and the high pressure exhaust channel.
Further advantages and embodiments of the pressure wave machine are defined in the dependent claims.